Ultrasonic studies of superconducting and magnetic transitions in La2 − xSrxCuO4 single crystal

Abstract Ultrasonic attenuation and sound velocity were measured at frequencies ranging from 25 to 305 MHz in a large single crystal of La 2 − x Sr x CuO 4 with nominal x of about 0.15. The observed features in attenuation and velocity suggest a relaxation process of magnetic origin at about 27 K, and those at ≈ 37.9 K orginate in the superconducting transition and a possible structural instability slightly above it.